Although dry eye is a disease that initially exhibits merely unpleasant symptoms such as dryness of the eyes or eyes that feel sandy or gritty, as the condition worsens, it causes considerable difficulties during the course of daily life. The number of the dry eye patients is increasing year by year with advent of an aging society and the increase in video display terminal (VDT) work such as personal computers, the estimated number of patients in the United States is over 10 million people, and in Japan, it is said to be more than 8 million people.
Although the pathology of dry eye is not completely clear, it is thought that the main cause is the decrease of lacrimal secretion and the increase of lacrimal evaporation accompanied by the decrease of the stability of the tear film. That is, these cause pathological symptom and/or findings such as eye discomfort, eye dryness, eye fatigue, hyperemia, keratoconjunctival epithelial disorders and the like. If these pathological symptoms and/or findings progress, vision abnormalities are ultimately generated, so that it is extremely important to treat the dry eye at an early stage and properly.
Wearing a soft contact lens leads to decrease in the stability of the tear film, so wearing soft contact lenses for dry eye patients may lead to exacerbation of dry eye symptoms. In addition, dry eye also may develop by wearing soft contact lenses. However, even with such a dry eye patient, there are cases where it is not desired to stop wearing soft contact lenses from the viewpoint of convenience.
On the other hand, in Japan, there are no widely recognized pharmaceuticals for treating onset and/or exacerbation of dry eye symptom caused by wearing soft contact lenses. Rather, in Japan, with regard to “DIQUAS® ophthalmic solution 3%”, “Hyalein® ophthalmic solution 0.1%” and “Hyalein® ophthalmic solution 0.3%” which have widely been used for dry eye patients, the use themselves for soft contact lens wearers is contraindicated.
By the way, the above-mentioned “DIQUAS® ophthalmic solution 3%” contains diquafosol tetrasodium salt at a concentration of 3% (w/v) as an active ingredient, and further contains benzalkonium chloride as a preservative. Diquafosol is a purinergic receptor agonist also called as P1,P4-di(uridine-5′) tetraphosphate or Up4U, and it has been known to have a lacrimation-promoting function as disclosed in Patent Document 1. However, it has not been known what effect diquafosol has on the onset and/or exacerbation of dry eye symptom caused by wearing soft contact lenses.